One previously known fuel cell stack is a solid oxide fuel cell (hereinafter may be abbreviated as an SOFC) stack that uses a solid electrolyte (solid oxide).
In such an SOFC, a fuel cell (power generating cell) used as a power generating unit includes, for example: an anode provided on one side of a solid electrolyte membrane and in contact with fuel gas; and an oxidant electrode (cathode) provided on the other side and in contact with oxidant gas (air). In addition, a fuel cell stack including a plurality of power generating cells stacked through interconnectors has been developed in order to obtain a desired voltage.
Such a type of fuel cell stack has a problem in that the temperature of power generating cells in a central region with respect to the direction of stacking the power generating cells (stacking direction) is generally higher than the temperature of power generating cells in end regions.
One technique proposed in view of this problem is to supply cold air to one side surface of the fuel cell stack in the central region with respect to the stacking direction and also supply heat-exchanged hot gas to the end portions, with respect to the stacking direction, of the fuel cell stack (see Patent Document 1).